Cationic lipids are amphipathic molecules having a lipophilic region containing one or more hydrocarbon groups, and a hydrophilic region containing at least one positively charged polar head group. Cationic lipids are useful, because cationic lipids facilitate entry of macromolecules such as nucleic acids into the cytoplasm through the cell plasma membrane by forming a positively charged (total charge) complex with macromolecules such as nucleic acids. This process, performed in vitro and in vivo, is known as transfection.
Patent Literatures 1 to 4 disclose cationic lipids and lipid particles containing the lipids, which are advantageous for delivering nucleic acids to cell in vivo, and for using nucleic acid-lipid particle compositions suitable for treatment of a disease. Patent Literature 1 discloses cationic lipids, for example,
2,2-dilinoleyl-4-(2-dimethylaminoethyl)-[1,3]-dioxolane (DLin-KC2-DMA), and the like. Patent Literature 2 discloses cationic lipids, for example,
(6Z,9Z,28Z,31Z)-heptatriaconta-6,9,28,31-tetraen-19-yl 4-(dimethylamino)butanoate (DLin-MC3-DMA), and the like. Patent Literature 3 discloses cationic lipids, for example,
1-methyl-3,3-bis{[(9Z,12Z)-octadeca-9,12-dien-1-yloxy]methyl}azetidine, and the like. Patent Literature 4 discloses cationic lipids, for example,
2-(1-methylpyrrolidin-2-yl)ethyl di[(9Z,12Z)-octadeca-9,12-dienyl]carbamate, and the like.